The present invention relates to an apparatus for the detection of substances and in particular explosive. It permits a non-destructive inspection of objects, such as parcels suspected of containing an explosive, by e.g. measuring the N/O ratio of said objects, said ratio providing a good signature of most explosives.
Bearing in mind the object liable to contain a substance such an explosive, it is necessary to be able to install the detection apparatus close to the object to establish whether or not it contains the substance in question.